Quote Originally Posted by Michael Mullan View Post
Rather than use the odbc connection app, I used SQL Server Management Studio, and it had no problem connecting.
I can ping the server by name or by IP.
I can connect with SSMS.
I can connect to the same application, in the same shared folder from different PC's in the same office, using the same DFCONNID.
I have good permissions in the folders.
I cant think of another test?
the error is about the server name and/or instance name

there are a few possibilities.

the server/instance name you are using in your connection id are incorrect
the server/instance name you are using in your connection id are correct but inaccessible
you are not using the connection id you think it is using

have you tried opening a table in dbexplorer?